Technical Field
Embodiments of the invention relate generally to magnetic resonance imaging. Particular embodiments relate to a system and method for securely connecting a cable to a gradient coil of a magnetic resonance imaging apparatus.
Discussion of Art
Magnetic resonance systems operate with coils for transmitting high-frequency pulses with nuclear resonance excitation and/or for receiving induced magnetic resonance signals. Typically, a magnetic resonance system has a superconducting coil to generate a basic magnetic field (B0) that is optimally homogeneous in an examination region, a whole body coil (also called body coil) installed at a fixed position for briefly imposing a pulsed RF field (B1) generally transverse to B0, and a number of small surface coils (also called local coils). To obtain information from which images of a patient can be generated, selected regions of the subject or patient to be examined are read out with gradient coils for each of three axes (e.g. X, Y roughly radial to the patient, Z in the longitudinal direction of the patient). The spatial coding in magnetic resonance tomography is achieved using a gradient coil system with three independently controllable, magnetically orthogonal gradient field coils. The gradient field coils may be collectively referred to as a “gradient coil.” By overlaying the three freely-scalable fields (in three directions X, Y, Z) the orientation of the coding plane (‘gradient field’) can be freely selected. Typically, this gradient coil is spatially fixed in a casting compound in which it is sealed.
A high current must be supplied to the gradient coil to generate the gradient fields. The currents are several hundred amperes; for instance, currents of 500-1300 A are typical. Previous attempts have been made to produce the connection of the gradient coil by means of a high-current coaxial connection formed of two plug elements, namely a plug and a mating connector that can be detachably connected with the plug. The plug is located at the coaxial cable conductor to be connected while the mating connector (thus the socket) is typically provided at the gradient coil. To connect, the plug on the end of the coaxial cable is inserted into the mating connector of the gradient coil and secured thereto utilizing hardware such as nuts and bolts or other threaded connections. Often times, the connection may require torqueing to relatively exact settings. Such existing means of connecting the current-carrying cable and the gradient coil, however, may result in unintended detachment of the cable from the gradient coil due to mechanical vibrations and/or alternating electromagnetic forces at the individual plug elements or at the conductor-side plug contact. In addition, with existing connection schemes, the cable typically extends axially away from the gradient coil due to the nature of the components utilized, which requires the cable to then be bent at a substantially ninety degree angle to bring it beyond the outside diameter of the magnet. Given the gauge of the cable utilized, however, such bending is not easy.
In view of the above, there is a need for a system and method for securely and reliably connecting a current-carrying cable to a gradient coil of a magnetic resonance imaging apparatus.